Businesses and consumers rely on their communications infrastructure to conduct business and to carry traffic for a variety of applications such as voice and data. Each enterprise subscribes to telecommunications services based on their need to handle a specific number of simultaneous calls to and from the enterprise. Calls within the enterprise are then handled using a Private Branch Exchange (PBX) system or network. Users of the PBX share the outside lines for making calls to destinations external to the enterprise and for receiving calls from sources outside the enterprise. The capacity through the PBX may be partitioned and dedicated for different purposes, e.g., for outbound calls, incoming calls, toll-free calls, etc. When a user of a PBX originates a telephone call, the PBX assigns an outside line and forwards the call towards the service provider's network. If a failure affects a trunk group being used for outbound calls (e.g., direct outbound dial), the PBX can utilize another trunk group. If a failure affects a trunk group being used for incoming traffic (e.g., direct inward dial), the network continues to forward traffic towards the failed trunk and the direct inward dial calls cannot be completed.
Therefore, there is a need for a method that provides a reliable path for direct inward dial calls.